i was only missing lucien's quest line, now its all good, however i have another question,
Nothing told you to put 13 points into it, but you should be more than fine. Those spells aren't strong, but no attack in this game is OP. There are not any further spells, but you also don't need anything stronger.
This game isn't hard combat wise, and if you find it is, there is always the cheat book. (It can be turned on even if you said no at the beginning. Not sure if there is a way in-game, but you can add the cheatbook in as an inventory item via a save editor.)
As far as what is the point of witch craft attribute, it is no different than any other of the talents, all of them exist to gatekeep a skill that unlocks once you get to a threshold. Each attribute exists to open up a reward once you get to a certain point, anything past that is pretty meaningless.
Chyos put a barrier to those spells behind a gate of a certain amount of witchcraft attribute, which makes sense story wise. The spells are a reward for labor, raising level to attribute points makes more sense that just about anything else. Killing wizards wouldn't necessarily teach you magic, but learning about magic does.
I don't think you can really tell much difference between an attack with strength 5 or strength 20. Enemies have different strengths and weaknesses, some have weaknesses to those spells. So it's not like you robbed yourself of anything but increasing intelligence. There is a good chance you could have already raised your intelligence above a fair threshold before getting the Gwen quests, introducing a new attribute means there is quest there, not just an automatic reward if you had consistently raised intelligence.
In my mind "what is the point of witchcraft attribute" is the exact same question of "what is the point of cutting onions" or "what is the point of bringing some wood and venison", which boils down to the object of every quest in every video game ever, "go get something you don't have, so you can either enjoy that something or trade it for something you do want."
I am sorry that you want some powerful magic spells and didn't get them. I promise you won't be running into any bosses you can't handle.